The next Mercedes-Benz E-Class may offer an inline-six engine, but that's not the only powertrain update coming to the automaker's popular midsize sedan. A new report from Autocar suggests inline-three and inline-four engines will be spun off the new engine architecture and make their way into international variants of the next-generation Mercedes E-Class and refreshed C-Class around 2016.

That three-cylinder may never show up in a U.S.-spec E-Class, but it might be offered in the refreshed 2017 C-Class. We wouldn’t be surprised to see the engine make it to the CLA-Class’ option list, either. The three-cylinder will be sufficiently refined to satisfy Mercedes customers, Autocar says. Also on the way, a new feature possibly called Autobahn Pilot is a semi-autonomous driving feature with an overtaking function.Also said to be in Mercedes' future is a new twin-turbo 4.0-liter V-8 that may replace the naturally aspirated 6.2-liter V-8 in the current C63 AMG, with all-wheel drive becoming an option. The seven-speed automatic will eventually be replaced by a new nine-speed unit.

Before the twin-turbo 4.0-liter shows up in the C-Class AMG model, the new engine could arrive in the 911-fighting Mercedes-Benz coupe that is rumored to take the place of the SLS AMG at the top of Mercedes' lineup. With an expected power output of just under 500 hp, the new Mercedes coupe has the Porsche 911 Turbo in its sights.Source: Autocar (1, 2)

These engines are getting way too small. If I were to buy a Mercedes-Benz or a BMW, I would not have a four or three cylinder engine. The E-Class is not a small car. Even the C-Class is not a light-weight; it is classified as an entry-level luxury car in the U.S., a compact executive car in the U.K. and a D-segment (mid-sized) car in the E.U. From what I've heard and noticed, the Ford Mondeo's, also in the D-segment, three-banger engine is very slow in the car. In my opinion, you buy a German car for reliability, power and refinement. Four cylinder engines do not offer the same refinement and smoothness as six and eight cylinder engines. Also, these new engines are not yet proven. At least BMW uses its proven I-6 and V-8 engines in everything it builds, and its I-4 is also all sorted out and behaves lovely. The smaller Benz engines scare me.

Both Mercedes and BMW built their reputations partly for the bulletproof and smoothe inlive 6 cylinder engines that easily go 250,000 miles if maintained. Four cylinders have to work harder and rev higher over their lives - so they don't last as long. Turbo-charging adds the stress of tremendous heat to the process - also impacting longer life....

I'd like to see some rigorous, scientifically-sound real-world testing on these new turbo small displacement engines vs. the bigger normally aspirated ones they are intended to replace to see what fuel economy gains are actually possible. I don't have any trouble believing that automakers game the standardized mpg tests and promise mileage not achievable in the real world. Anti-Christ Consumer Reports has been having a hell of a time getting the claimed fuel economy out of Ford's 1.6 and 2.0 Ecoboost. Long-term durability is going to take years to decipher, though.

@Emajor75@TheClassicCarFactory "Anti-Christ Consumer Reports." Hilarious! Indeed true, most current turbo models don't hit EPA estimates, including Audi's 2.0 T. However, there are some exceptions. The 09 Legacy GT with a 5 spd slush-box I had for 3 yrs as a lease, never had reliability problems, and always yielded better than the estimated mileage stated. I drive 20 miles one way on the parking lot known as the 101 Hollywood freeway every morning, and still managed 25.6 combined. In addition, some co-workers with the turbo i4 3 Series also state their fuel economy is better than expected. As you stated though, I have not heard of anyone with Ford's eco-boost engines that come close to the listed numbers.

@Emajor75 @TheClassicCarFactory Apart from ford eco boost engines , I disagree with you, there are quite a few vehicle that get the stated MPG, there might be some factors such as ethanol, most turbo does not lost long on ethanol mix gasoline.But aside form that, the nissan juke, subaru turbo,mitsubishi turbo and the bmw turbo 3 series did meet EPA MPG when test by CR, check fuelly the chevy cruze is averaging very high too.

I think you're right, I've been hearing so much about underperforming Ecoboosts and the movement to replace V6s in family sedans w/ 2.0 turbos that I had forgotten there are some good examples out there already of turbos turning in the advertised numbers. VWs 1.8t looks like it will have no trouble surpassing the 2.5 5 -cylinder's mileage as well. BMWs 2.0t sounds like a mixed blessing; certainly better mileage and even better acceleration, but sounds like it has lost the trademark refinement and zing their non-turbo inline 6s were known for.

While I'd normally be less than thrilled to hear about a new four cylinder, or God help us three cylinder, engine to power a hefty RWD mid-size sedan the inline six news more than makes up for it. I'm looking forward to seeing this new six in a row and bet it will make for a more efficient (but likely no more affordable) entry level engine for the S and SL Class as well.